Nuclear Theory·nucl-th

Friday·May 29, 2020

11 papers—2 primary·9 cross-listed

03
[Submitted on 27 May 2020] (cross-list from hep-ph)
Explaining $b \to s ℓ^{+} ℓ^{-}$ and the Cabibbo Angle Anomaly with a Vector Triplet
Bernat Capdevila🇮🇹 · Andreas Crivellin🇨🇭 · Claudio Andrea Manzari🇨🇭 · Marc Montull🇨🇭
The most statistically significant hints for new physics in the flavor sector are discrepancies between theory and experiment in $B$ decays to lepton pairs ( $b \to s ℓ^{+} ℓ^{-}$ ) and a deficit in $1^{st}$ row CKM unitarity (the Cabibbo Angle anomaly). We propose that these anomalies can be reconciled by a simplified model with massive gauge bosons transforming in the adjoint representation of $S U (2)_{L}$ . After calculating the impact of this model on $B$ decays, observables testing charged current lepton flavor universality (LFU), electro-weak precision observables and LHC searches we perform a global fit to all available data. We find that our model can provide a consistent common explanation of both anomalies and that the fit to the data is more than $7 σ$ better than the fit of the SM. The model also predicts interesting correlations between LFU violation in the charged current and $b \to s ℓ^{+} ℓ^{-}$ data which can be tested experimentally in the near future.
Comments:
13 pages, 4 figures, 2 tables; version accepted for publication in Physical Review D
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); High Energy Physics — Lattice (hep-lat); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
2005.13542 [pdf]
PRD(2021)·81 citations
04
[Submitted on 28 May 2020] (cross-list from hep-ph)
Quasi parton distribution functions at NNLO: flavor non-diagonal quark contributions
Long-Bin Chen🇨🇳 · Wei Wang🇨🇳 · Ruilin Zhu🇨🇳
We present a next-to-next-to-leading order (NNLO) calculation of the quasi parton distribution functions (Quasi-PDFs) in the large momentum effective theory (LaMET). We focus on the flavor non-diagonal quark-quark channel and demonstrate the LaMET factorization at the NNLO accuracy in the modified minimal subtraction scheme. The matching coefficient between the quasi-PDF and the light-cone PDF is derived. This provides a first step towards a complete NNLO analysis of quasi-PDFs and to better understand the nucleon structures from the first principle of QCD.
Comments:
10 pages, 3 figures; v2: accepted for publication in Physical Review D as a rapid communication
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); High Energy Physics — Lattice (hep-lat); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
2005.13757 [pdf]
PRD(2020)·38 citations
05
[Submitted on 28 May 2020] (cross-list from hep-lat)
Moments of nucleon isovector structure functions in $2 + 1 + 1$ -flavor QCD
Santanu Mondal🇺🇸 · Rajan Gupta🇺🇸 · Sungwoo Park🇺🇸 · Boram Yoon🇺🇸 · Tanmoy Bhattacharya🇺🇸 · Huey-Wen Lin🇺🇸
We present results on the isovector momentum fraction, $⟨ x ⟩_{u - d}$ , helicity moment, $⟨ x ⟩_{Δ u - Δ d}$ , and the transversity moment, $⟨ x ⟩_{δ u - δ d}$ , of the nucleon obtained using nine ensembles of gauge configurations generated by the MILC collaboration using $2 + 1 + 1$ -flavors of dynamical highly improved staggered quarks (HISQ). The correlation functions are calculated using the Wilson-Clover action and the renormalization of the three operators is carried out nonperturbatively on the lattice in the RI $^{'}$ -MOM scheme. The data have been collected at lattice spacings $a \approx 0.15, 0.12, 0.09,$ and 0.06 fm and $M_{π} \approx 310, 220$ and 135 MeV, which are used to obtain the physical values using a simultaneous chiral-continuum-finite-volume fit. The final results, in the $M S$ scheme at 2 GeV, are $⟨ x ⟩_{u - d} = 0.173 (14) (07)$ , $⟨ x ⟩_{Δ u - Δ d} = 0.213 (15) (22)$ and $⟨ x ⟩_{δ u - δ d} = 0.208 (19) (24)$ , where the first error is the overall analysis uncertainty and the second is an additional systematic uncertainty due to possible residual excited-state contributions. These results are consistent with other recent lattice calculations and phenomenological global fit values.
Comments:
18 pages, 8 figures. Final published version
Subjects:
High Energy Physics — Lattice (hep-lat); Nuclear Theory (nucl-th)
arXiv:
2005.13779 [pdf]
PRD(2020)·37 citations
06
[Submitted on 28 May 2020] (cross-list from hep-th)
Finite-Density Massless Two-Color QCD at Isospin Roberge-Weiss Point and 't Hooft Anomaly
Takuya Furusawa🇯🇵 · Yuya Tanizaki🇯🇵 · Etsuko Itou🇯🇵
We study the phase diagram of two-flavor massless two-color QCD (QC $_{2}$ D) under the presence of quark chemical potentials and imaginary isospin chemical potentials. At the special point of the imaginary isospin chemical potential, called the isospin Roberge--Weiss (RW) point, two-flavor QC $_{2}$ D enjoys the $Z_{2}$ center symmetry that acts on both quark flavors and the Polyakov loop. We find a $Z_{2}$ 't Hooft anomaly of this system, which involves the $Z_{2}$ center symmetry, the baryon-number symmetry, and the isospin chiral symmetry. Anomaly matching, therefore, constrains the possible phase diagram at any temperatures and quark chemical potentials at the isospin RW point, and we compare it with previous results obtained by chiral effective field theory and lattice simulations. We also point out an interesting similarity of two-flavor massless QC $_{2}$ D with $(2 + 1)$ d quantum anti-ferromagnetic systems.
Comments:
23 pages, 2 figures, 2 appendices. v2: references are updated
Subjects:
High Energy Physics — Theory (hep-th); Strongly Correlated Electrons (cond-mat.str-el); High Energy Physics — Lattice (hep-lat); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2005.13822 [pdf]
PRResearch(2020)·10 citations
07
[Submitted on 28 May 2020] (cross-list from math-ph)
Fock space dualities
K. Neergård
A general theorem due to Howe of dual action of a classical group and a certain non-associative algebra on a space of symmetric or alternating tensors is reformulated in a setting of second quantization, and familiar examples in atomic and nuclear physics are discussed. The special case of orthogonal-orthogonal duality is treated in detail. It is shown that, like it was done by Helmers more than half a century ago in the analogous case of symplectic-symplectic duality, one can base a proof of the orthogonal-orthogonal duality theorem and a precise characterization of the relation between the equivalence classes of the dually related irreducible representations on a calculation of characters by combining it with an analysis of the representation of a reflection. Young diagrams for the description of equivalence classes of irreducible representations of orthogonal Lie algebras are introduced. The properties of a reflection of the number non-conserving part in the dual relationship between orthogonal Lie algebras corroborate a picture of an almost perfect symmetry between the partners.
Comments:
A reference corrected
Subjects:
Mathematical Physics (math-ph); math.MP (math.MP); Nuclear Theory (nucl-th); Atomic Physics (physics.atom-ph)
arXiv:
2005.13843 [pdf]
J.Math.Phys.(2020)·4 citations
08
[Submitted on 28 May 2020] (cross-list from nucl-ex)
Studies of dense nuclear matter at NICA
Peter Senger🇩🇪
Laboratory experiments with high-energetic heavy-ion collisions offer the opportunity to explore fundamental properties of nuclear matter, such as the high-density equation-of-state, which governs the structure and dynamics of cosmic objects and phenomena like neutron stars, supernova explosions, and neutron star mergers. A particular goal and challenge of the experiments is to unravel the microscopic degrees-of-freedom of strongly interaction matter at high density, including the search for phase transitions, which may feature a region of phase coexistence and a critical endpoint. As the theory of strong interaction is not able to make firm predictions for the structure and the properties of matter high baryon chemical potentials, the scientific progress in this field is driven by experimental results. The mission of future experiments at FAIR and NICA, which will complement the running experimental programs at GSI, CERN, and RHIC, is to explore new diagnostic probes, which never have been measured before at collision energies, where the highest net-baryon densities will be created. The most promising observables, which are expected to shed light on the nature of high-density QCD matter, comprise the collective flow of identified particles including multi-strange (anti-) hyperons, fluctuations and correlations, lepton pairs, and charmed particles. In the following, the perspectives for experiments in the NICA energy range will be discussed.
Comments:
23 pages, 21 figures, Physics introduction to the Technical Design Report on the Inner Tracking System of the MPD experiment at NICA
Subjects:
Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
2005.13856 [pdf]
8 citations
09
[Submitted on 28 May 2020] (cross-list from hep-lat)
Pion and Kaon Distribution Amplitudes in the Continuum Limit
Rui Zhang🇺🇸 · Carson Honkala🇺🇸 · Huey-Wen Lin🇺🇸 · Jiunn-Wei Chen🇹🇼
We present a lattice-QCD calculation of the pion, kaon and $η_{s}$ distribution amplitudes using large-momentum effective theory (LaMET). Our calculation is carried out using three ensembles with 2+1+1 flavors of highly improved staggered quarks (HISQ), generated by MILC collaboration, at 310 MeV pion mass with 0.06, 0.09 and 0.12 fm lattice spacings. We use clover fermion action for the valence quarks and tune the quark mass to match the lightest light and strange masses in the sea. The resulting lattice matrix elements are nonperturbatively renormalized in regularization-independent momentum-subtraction (RI/MOM) scheme and extrapolated to the continuum. We use two approaches to extract the $x$ -dependence of the meson distribution amplitudes: 1) we fit the renormalized matrix elements in coordinate space to an assumed distribution form through a one-loop matching kernel; 2) we use a machine-learning algorithm trained on pseudo lattice-QCD data to make predictions on the lattice data. We found the results are consistent between these methods with the latter method giving a less smooth shape. Both approaches suggest that as the quark mass increases, the distribution amplitude becomes narrower. Our pion distribution amplitude has broader distribution than predicted by light-front constituent-quark model, and the moments of our pion distributions agree with previous lattice-QCD results using the operator production expansion.
Subjects:
High Energy Physics — Lattice (hep-lat); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2005.13955 [pdf]
PRD(2020)·95 citations
10
[Submitted on 28 May 2020] (cross-list from astro-ph.HE)
Astrophysical Implications of Neutron Star Inspiral and Coalescence
John L. Friedman🇺🇸 · Nikolaos Stergioulas🇬🇷
The first inspiral of two neutron stars observed in gravitational waves was remarkably close, allowing the kind of simultaneous gravitational wave and electromagnetic observation that had not been expected for several years. Their merger, followed by a gamma-ray burst and a kilonova, was observed across the spectral bands of electromagnetic telescopes. These GW and electromagnetic observations have led to dramatic advances in understanding short gamma-ray bursts; determining the origin of the heaviest elements; and determining the maximum mass of neutron stars. From the imprint of tides on the gravitational waveforms and from observations of X-ray binaries, one can extract the radius and deformability of inspiraling neutron stars. Together, the radius, maximum mass, and causality constrain the neutron-star equation of state, and future constraints can come from observations of post-merger oscillations. We selectively review these results, filling in some of the physics with derivations and estimates.
Comments:
52 pages, 13 figures, corresponds to the published version in IJMPD, with the addition of an expanded version of Section 4 on tidal deformabilities and of a new Section 7 on the measurement of the Hubble constant. Notice that the remaining text contains the original citations of the published version
Subjects:
High Energy Astrophysical Phenomena (astro-ph.HE); General Relativity and Quantum Cosmology (gr-qc); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2005.14135 [pdf]
Int.J.Mod.Phys.D(2020)·26 citations
11
[Submitted on 28 May 2020] (cross-list from astro-ph.HE)
Equation of state constraints from nuclear physics, neutron star masses, and future moment of inertia measurements
S. K. Greif · K. Hebeler · J. M. Lattimer · C. J. Pethick · A. Schwenk
We explore constraints on the equation of state (EOS) of neutron-rich matter based on microscopic calculations up to nuclear densities and observations of neutron stars. In a previous work we showed that predictions based on modern nuclear interactions derived within chiral effective field theory and the observation of two-solar-mass neutron stars result in a robust uncertainty range for neutron star radii and the EOS over a wide range of densities. In this work we extend this study, employing both the piecewise polytrope extension from Hebeler et al. as well as the speed of sound model of Greif et al., and show that moment of inertia measurements of neutron stars can significantly improve the constraints on the EOS and neutron star radii.
Comments:
11 pages, 10 figures, published version
Subjects:
High Energy Astrophysical Phenomena (astro-ph.HE); Solar and Stellar Astrophysics (astro-ph.SR); Nuclear Theory (nucl-th)
arXiv:
2005.14164 [pdf]
ApJ(2020)·86 citations

Affiliations

first authorsco-authorsvia INSPIRE